Various apparatus and methods for intravascular ultrasound imaging and atherectomy have been known and used in the past. Yock, U.S. Pat. No. 5,000,185, describes a method and catheter for performing intravascular two-dimensional ultrasonography and recanalization. Methods of vascular intervention by mechanical cutting have been described in Gifford et al., U.S. Pat. No. 4,669,469, Kensey, U.S. Pat. No. 4,700,705, Pope, U.S. Pat. No. 4,899,757, and Auth, U.S. Pat. No. 4,990,134. In addition, U.S. Pat. No. 4,794,931 further describes a single catheter with combined imaging and cutting capability.
These known apparatus and methods all use a rotating imaging or cutting element at the distal end of a catheter. By rotating the imaging element, for example, a transducer or a transducer/reflector assembly, a real time ultrasound image in the plane perpendicular to the vessel can be obtained. This 360.degree. view of the vessel enables a physician to differentiate tissue structure and fatty deposits in the vessel wall. By moving the entire catheter or the imaging element in the longitudinal direction, a three-dimensional view of the artery can be formed.